1. Field of the Invention
The present invention relates to a data processing apparatus and a parameter generating apparatus suitable for use in creating audio sources to be reproduced on a surround system. The present invention also relates to a computer program applied to these apparatuses.
2. Description of the Related Art
Assume that a sound emitting point at which a sound is emitted and a sound receiving point at which the sound is received are placed in an acoustic space such as a room having a rectangular parallelepiped shape. The sound receiving point is a human, microphone or the like. In this case, sounds emitted from the sound emitting point reflect on various parts of the acoustic space before reaching the sound receiving point. Disclosed in Japanese Patent Laid-Open Publication No. 2004-212797 and Japanese Patent Laid-Open Publication No. 2004-312109 are apparatuses for simulating such propagation of sounds to the sound receiving point on a computer to reproduce on a 4-channel stereo system. In FIG. 1A, for example, respective speakers 52L, 52R, 52SR, 52SL are placed at positions that correspond to the four corners of a square, with a listener centered thereon. Assume that the listener is placed at a sound receiving point 106 with a hypothetical sound emitting point 104 placed in the direction of the midpoint between the speakers 52L, 52R, and the sound pressure level of a direct sound reaching the sound receiving point 106 from the sound emitting point 104 is P. According to the art described in Japanese Patent Laid-Open Publication No. 2004-212797, a direct sound emitted from the hypothetical sound emitting point 104 can be simulated by emitting a sound having the sound pressure level of “P/2” from the respective speakers 52L, 52R to the sound receiving point 106. In FIG. 1A, reflected sounds are omitted.
In Japanese Patent Laid-Open Publication No. 2004-312109, furthermore, there is disclosed an art for changing the level of audio signals on a 4-channel stereo system in accordance with “the orientation of a sound receiving point”. Assume that the sound receiving point is a “human”, for example. In this case, the sound pressure perceived by the human ears varies between a case in which the human hears a sound having a sound pressure P from the front and a case in which the human hears the sound from the back. In this art, therefore, the orientation of the sound receiving point is taken as a parameter to change the level of audio signals. In Japanese Patent Laid-Open Publication No. 2004-312109, furthermore, there is also disclosed an art in which a sound emitting point and a sound receiving point are placed at an arbitrarily chosen position in an acoustic space, and the sound emitting point is automatically moved along a given path. In U.S. Pat. No. 5,636,283, furthermore, there is disclosed an art which allows a user to arbitrarily specify a course along which a sound emitting point moves, and reproduces the move of the sound emitting point along the course on a 4-channel stereo system.
In Japanese Patent Laid-Open Publication No. 2003-271135, there is disclosed an art for rotating a sound field to be reproduced by a multi-channel reproducing apparatus by given angle. This is achieved by mixing multi-channel signals in a mixing ratio corresponding to the rotation angle. Assuming that in FIG. 1B having audio signals S_L, S_R, S_SR, S_SL that form a 4-channel stereo system, for example, audio signals realizing a sound field that is rotated 45 degrees to the right are emitted from respective speakers 52L, 52R, 52SR, 52SL. In this case, each of the original audio signals S_L, S_R, S_SR, S_SL is mixed with its neighboring audio signal in the ratio of “½” to emit the resultant audio signals S_L′, S R′, S SR′, S SL′ from the speakers 52L, 52R, 52SR, 52SL. In the arts described in Japanese Patent Laid-Open Publication No. 2004-212797 and Japanese Patent Laid-Open Publication No. 2004-312109, the orientation of the sound receiving point 106 is utilized in order to determine the level of sounds to be delivered to the sound receiving point 106, however, it is not utilized in order to determine the localization between the speakers. More specifically, the orientation of the sound receiving point 106 is limited to predetermined directions. To determine the localization between the speakers in accordance with the orientation of the sound receiving point 106, therefore, the art disclosed in Japanese Patent Laid-Open Publication No. 2003-271135 is also required. Assume that in FIG. 1A, for example, the sound receiving point 106 is a human with his face rotating 45 degrees to the left. In a case where sounds to be delivered to the sound receiving point 106 are simulated for a listener in a listening room, if the listener in the listening room faces the front, the sound field can be simulated by rotating the entire sound field 45 degrees to the right. In this case, the sound image of the sound emitting point 104 has to be placed to the direction of the speaker 52R when viewed from the listener.
If the sound field is rotated by use of the art disclosed in Japanese Patent Laid-Open Publication No. 2003-271135, the sound pressure from the respective speakers are: S_L′=P/4 in the speaker 52L, S_R′=P12 in the speaker 52R, S_SR′=P/4 in the speaker 52SR. Although the above sound pressure brings agreement between the center of the sound image and the orientation of the speaker 52R and makes the total sum of the sound pressure agree with “P”, there still exists a problem that the sound image sounds blurred because a sound that simulates the sound emitting point 104 is separated to be output from the three speakers. In addition, there is another problem that complicated calculation is required to rotate a sound field by use of the art disclosed in Japanese Patent Laid-Open Publication No. 2003-271135 after generation of multi-channel signals by use of the arts disclosed in Japanese Patent Laid-Open Publication No. 2004-212797 and Japanese Patent Laid-Open Publication No. 2004-312109.
In some cases, furthermore, a change in the size of the acoustic space is required, with relative layout of the sound emitting point 104 and the sound receiving point 106 in the acoustic space being maintained. In such cases, however, on using the arts disclosed in Japanese Patent Laid-Open Publication No. 2004-312109 and U.S. Pat. No. 5,636,283, a user is required quite complicated operations such as specifying the size of the acoustic space and the position of the sound emitting point 104 and the sound receiving point 106 individually. Therefore, it is convenient for the user if the user can intuitively grasp, on a screen, the relationship between the acoustic space and the simulated settings in which a listener is listening contents in a listening room.
In other cases, furthermore, a plurality of elements such as the sound emitting point 104 and the sound receiving point 106 in the acoustic space are required to move at one time with given relationship between the elements being maintained. When the arts disclosed in Japanese Patent Laid-Open Publication No. 2004-312109 and U.S. Pat. No. 5,636,283 are used, however, complicated operations are required such as moving the sound emitting point 104 and the sound receiving point 106 individually.